1. Field of the Invention
The present invention relates to the noninvasive, remote sensing of predetermined parameters such as, for example, remote sensing of human body temperature.
2. Background of the Related Art
Internal body temperature is a physiologic variable that is precisely controlled by the body. Chemical processes and enzymes required to catalyze the associated chemical reactions, thereby regulating cellular function, optimally operate within this narrow thermal bandwidth. Thermoregulation encompasses all physiological processes and responses that balance heat production and heat loss to maintain body temperature within this normal range. Compared to the adult or older pediatric model, thermoregulation is even more critical to neonatal care.
Compared to adults, newborns are particularly vulnerable to temperature extremes. If heat loss is not preempted, newborns could suffer the ill effects of cold stress or hypothermia. Depending on the gestational age, mortality may increase by 10% for each degree Celsius (° C.) that a baby's body temperature is below 36° C. Conversely, at relatively high temperatures, infants may be subjected to the dangers of heat stress or hyperthermia. Both types of thermal stresses, hypo- and hyperthermia can be a significant cause of morbidity and mortality in this vulnerable population. Thus, in the hospital setting, infant incubators are designed to keep the infant in an environment of constant temperature.
Nonetheless, providing optimal thermal conditions to the newborn require the body temperature to be measured. To date, wired thermistors are conventionally employed that are attached to a neonate's skin using a strong adhesive to keep them in place. However, adhesive use on the thermistor probe cover is not an innocuous intervention. Investigations have shown increased microbial growth beneath probe covers, some of which have proved to be pathogenic. Others have found skin impairment ranging from chemical sensitivities to prolonged mechanical force on the skin from some adhesives. Adhesives can irritate the skin by occlusion or by altering the skin morphology via epidermal stripping. The removal of adhesively-attached skin temperature probes can result in “skin tears” in which shear or frictional forces separate the dermis from the epidermis.
These tears can compromise skin barrier function, cause a marked increase in transepidermal water loss and, in many cases, disrupt the skin's ability to protect against microorganism invasion. Especially for extremely premature neonates, the adhesive poses a high potential risk of injury due to their immature skin. Studies have shown that at 24 weeks gestation, premature neonates have little stratum corneum and attenuated rete ridges. Their skin is red, wrinkled, translucent, and gelatinous in appearance. They lack subcutaneous tissue, therefore, their dermis is lying directly over the muscle. Consequently, skin stripping secondary to adhesive dressing and/or tape removals can result in full-thickness tissue loss.
Even at 36 weeks (full term), the epidermal and dermal layers of neonates, although structurally similar to an adult, are just up to 60% as thick as those in an adult. As a result, epidermal stripping secondary to tape and adhesive dressing removal is most common in neonates born before 27 weeks gestation and is the primary cause of skin breakdown in the Neonatal Intensive Care Unit (NICU). Given the neonate's attenuated rete ridges, adhesive products typically bond more aggressively to the epidermis than the epidermis does to the dermis. Consequently, epidermal stripping is not only a source of discomfort, but can also lead to other morbidity in very low birth weight neonates and those who are immune-compromised.
Skin friendly adhesives that can hold the wired probe in place while minimizing trauma to the skin have not yet been developed. Alternative temperature probes that can eliminate adhesives also are nonexistent. In addition, remote thermal-imaging systems that may offer non-adhesive, non-contact features and a resolution of 0.3° C. are still too expensive for general use in the NICU.